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As we know there is a design flaw on the WD21 which causes the rear seat floor to rust out. You won't see the rust "until it's too late" - the reason being there are multiple reinforcement plates in this area and it's rusting from the inside-out due to water ingress between the plates. Everyone should have this issue although it's going to be exaggerated if you live in the rust belt. I believe I have identified where the water is coming from. There is a chassis cross channel at the top of the trunk floor that contains ventilation holes. Based on the mud splash pattern under the car I believe the rotating drive shaft is throwing water up into these ventilation holes. This water is then creeping down between the reinforcement plates and getting trapped. There is a second possible entry point on the sides of the plate which also have ventilation holes and may be taking in water from the rear tires; although when I cut out the top layer of reinforcement plates to investigate I noted the passenger side was much worse than the driver side - again I believe due to the rotating drive shaft. Here is a picture (taken from where the fuel tank would be which I have removed at the moment). Pathfinder Rust Spot 1.jpg The preventative fix would be to shoot cavity wax into this area. I used Noxudol 750 which comes with a 360 degree 2' extension wand and has a high creep rate and anti-corrosion properties. After saturating the length of this channel very well with wax and waiting a bit - sure enough the wax started to drip out of the same areas that typically rust out between the plates. Pathfinder Rust Spot 2.jpg Another preventative may be to JB Weld some stand-off baffle plates over the ventilation holes (you don't want to plug the holes) which should stop any further water entry. Lastly, a 3rd possible entry point are the lower rear seat belt bolts which penetrate the plates and into the rear wheel well. I didn't see as much evidence of this; however I removed these bolts, applied anti-seize and reinstalled them for good measure.

I had no idea that section of the floor was double-walled! Makes sense, though--rust loves metal sandwiches, especially once dirt and moisture get in there. I went and had a look at mine, and it doesn't have the hole in the middle, but it does have a couple of holes above each spring perch. My floor is solid so far (under the seats, at least), but I may copy what you've done with the wax to keep it that way. I'm tempted to try and find rubber bungs to fill those holes when I'm done. If the top is closed up, and the bottom is open enough to leak wax, surely that's enough ventilation, right? No sense leaving them open for stuff to get in that might not be able to get out. I'm convinced that's what killed the frame on my '95--it's easier for dirt to get into the frame than it is for it to get out, so it just sits in there, clogs up the drains, and forms a wet (and salty, given where that truck was from) sponge up against the steel. Edit: I looked up the wax spray you're using, and the Amazon link says it's "restorative scalp and hair care."

I would be surprised if there isn't some rubber strip material out there that could be cut to size and stuck on.

I should have posted here first. Normally when I try unplugging something it has unintended consequences. This doesn’t appear to have any thus far! Thank you. Full manual definitely has some annoying drawbacks, but I really like not worrying about draining my battery or having to disconnect the battery or some unexpected actuation of the locks. Thank you! Sent from my iPhone using Tapatalk

I don't think that strip is factory. Probably an aftermarket add-on to prevent door dings.